1. Field of the Invention
The present invention relates to a video data transmitting system and, more particularly, to a video data transmission system in which data is band compressed by means of what is called a block encoding and is transmitted.
2. Related Background Art
In a system in which a color television signal is separated into a luminance signal and a chrominance signal and digitized and transmitted, in general, a data sync block consisting of one sync signal pattern, the luminance signal, the chrominance signal, and a parity indication for detection of data errors is transmitted as a unit. The television signal of one field or one frame is divided and transmitted on such a sync block unit basis. In the television signal, the band of the chrominance signal is m/n (m&lt;n; m and n are positive integers) times that of the luminance signal and the data amounts of the luminance signal and chrominance signal are set to ratio n:m. In consideration of this fact, in the conventional transmitting system, the data amounts of the luminance signal and chrominance signal included in one sync block have been set to ratio n:m so that both the luminance signal and the chrominance signal of the corresponding picture plane portion can be reproduced from one sync block on the receiving side (reproducing side).
However, in the system for transmitting data on a sync block unit basis as mentioned above, the data amount in the sync block depends on a data length of each sync block and is determined by the probability of detection of the sync block upon reproduction and the size of area corresponding to one sync block on the reproducing picture plane. That is, when the detection probability of the sync block is low because of the quality of the transmission path, the data amounts of the luminance signal and chrominance signal in the sync block are set to small values so as not to increase interference which is exerted on the reproducing picture plane.
In recent years, as a highly efficient band compressing system of a television signal, what is called a block encoding method of encoding all pixels constructing a picture plane on a unit basis of a pixel block consisting of a plurality of pixels has been proposed. For instance, such a block encoding method has been also proposed in U.S. patent applications which have recently been filed by the assignee of the present invention. However, in the conventional construction of the sync block, no consideration is given to the above block encoding method and such a construction is improper for the block encoding method.